Warp transfer control system of loom for filling density change

Abstract

A warp transfer control system for a loom, includes a first actuator for varying a warp let-off speed, a second actuator for varying a fabric take-up speed to change a filling density, and a control unit which has a take-up control section for controlling the second actuator, a feedback control section for controlling the let-off speed through the first actuator when no change is required in the filling density, and a feedforward control section for changing the let-off speed so as to improve an appearance quality of a fabric when the density is changed. When a change from a first filling density to a second density is required, the feedforward section first changes the let-off speed excessively from a first let-off speed corresponding to the first density beyond a second let-off speed corresponding to the second density, and holds the let-off speed at such an excessive level for a limited duration.

What is claimed is: 
     
       1. A control system of a loom, comprising: warp transfer means for transferring warp Yarns in said loom, said warp transfer means comprising warp let-off means including first drive means for varying a warp let-off means including first drive means for varying a warp let-off rate, and fabric take-up means including second drive means for changing a fabric take-up rate of said loom to change a filling density of a woven fabric,   command means for commanding changes of said filling density in accordance with a preset filling density pattern during a normal weaving operation, and   control means for controlling said warp let-off rate and said fabric take-up rate by producing a warp let-off rate control signal representing said warp let-off rate, and a fabric take-up rate control signal representing said fabric take-up rate in such a manner that, each time a change of said filling density is commanded by said command means, said let-off control signal is changed from a current let-off signal value to an excessive let-off signal value at a first instant, said take-up control signal is changed from a current value directly to a new take-up signal value at a second instant, and said let-off control signal is further changed at a third instant from said excessive let-off signal value to a new let-off signal value which is intermediate between said current let-off signal value and said excessive let-off signal value.   
     
     
       2. A control system according to claim 1 wherein said control system further comprises first sensing means for sensing an actual warp tension of said warp yarns, and said control means comprises feedback controlling means for controlling said warp let-off rate so as to reduce a deviation of said actual warp tension sensed by said sensing means, from a predetermined desired warp tension. 
     
     
       3. A control system according to claim 2 wherein said control means further comprises feedforward controlling means for changing said warp let-off rate from a current let-off rate value to an excessive let-off rate value, holding said let-off rate equal to said excessive let-off rate value for a predetermined limited duration, and changing said let-off rate to a new intermediate let-off rate value which is between said current let-off rate value and said excessive let-off rate value when a change of said filling density is commanded, said control means including means for preventing said feedback controlling means from controlling said warp let-off rate for said limited duration. 
     
     
       4. A control system according to claim 3 wherein said control means includes means for changing said let-off control signal and said take up control signal in such a time sequence that said first instant is earlier than said second instant, and said second instant is earlier than said third instant. 
     
     
       5. A control system according to claim 3 wherein said control system further comprises second sensing means for detecting revolutions of a main shaft of said loom to count repetitions of a weaving cycle, and said command means is connected with said second sensing means. 
     
     
       6. A warp transfer control method for changing a filling density during a normal weaving operation of a loom, comprising steps of: producing a command signal to command a change of said filling density to a new density value,   changing a warp let-off rate to an excessive let-off rate value beyond a theoretical let-off rate value corresponding to said new density value upon receipt of said command signal, and holding said warp let-off rate equal to said excessive value for a predetermined limited time duration,   changing a fabric take-up rate to a new take-up rate value to change said filling density to said new density value, and   varying said warp let-off rate from said excessive let-off value toward said theoretical value after said limited time duration expires.   
     
     
       7. A warp transfer control system for changing a filling density during a normal weaving operation of a loom, comprising; a warp let-off mechanism including first drive means for varying a warp let-off rate in accordance with a warp let-off rate control signal,   a fabric take-up mechanism including second drive means for changing a fabric take-up rate in accordance with a fabric take-up rate control signal,   command means for commanding changes of the filling density of a woven fabric in accordance with a preset filling density pattern during the normal weaving operation by producing a command signal to command a change of the filling density to a new density value each time a change of the filling density is required, and   control means for producing said warp let-off rate control signal and said fabric take-up rate control signal, said control means including means for changing said warp let-off rate to an excessive let-off rate value beyond a theoretical let-off rate value corresponding to said new density value upon receipt of said command signal, holding said warp let-off rate equal to said excessive value for a predetermined limited time duration, changing said fabric take-up rate to a new take-up rate value to change the filling density to said new density value, and varying said warp let-off rate from said excessive let-off value toward said theoretical value after said limited time duration expires.   
     
     
       8. A control system according to claim 7 wherein said control means includes means for changing said warp let-off rate from a current let-off rate value to said excessive let-off rate value by such an amount of change that said theoretical let-off rate value is intermediate said current let-off rate value and said excessive let-off rate value. 
     
     
       9. A control system according to claim 7 wherein said control means includes means for decreasing said warp let-off rate from said excessive let-off rate value by such an amount that said excessive let-off rate value is lower than said theoretical let-off rate value corresponding to said new filling density value when an increase of the filling density to said new density value is commanded, and increasing said warp let-off rate to said excessive let-off rate value by such an amount that said excessive let-off rate value is higher than said theoretical let-off rate value corresponding to said new density value when a decrease of the filling density to said new density value is commanded.